Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$72.46	13.171%	$82.0037	$82.00	$82.00	$82.00
Purchase #2	$96.88	13.314%	$109.7786	$109.78	$109.80	$109.80
Purchase #3	$27.75	13.302%	$31.4413	$31.44	$31.45	$31.40
Purchase #4	$150.30	12.140%	$168.5464	$168.55	$168.55	$168.50
Purchase #5	$215.44	8.517%	$233.789	$233.79	$233.80	$233.80
Purchase #6	$42.70	12.576%	$48.07	$48.07	$48.05	$48.10
Purchase #7	$38.63	5.290%	$40.6735	$40.67	$40.65	$40.70
7 purchase totals =	$644.16		$714.3025	$714.30	$714.30	$714.30